Gelastic Material
In U.S. Pat. No. 7,076,822; Pearce discloses that gelastic materials “are low durometer thermoplastic elastomeric compounds and viscoelastomeric compounds which include . . . an elastomeric block copolymer component and a plasticizer component. [A plasticizer is a hydrocarbon molecule which associates with the material into which they are incorporated. Additives can also be inserted into the formulation to obtain specific qualities.]
The elastomer component of the example gel material includes a triblock polymer of the general configuration A-B-A, wherein the A represents a crystalline polymer such as a mono alkenylarene polymer, including but not limited to polystyrene and functionalized polystyrene, and the B is an elastomenc polymer such as polyethylene, polybutylene, poly(ethylene/butylene), hydrogenated poly(isoprene), hydrogenated poly(butadiene), hydrogenated poly(isoprene+butadiene), poly(ethylene/propylene) or hydrogenated poly(ethylene/butylene+ethylene/propylene), or others. The A components of the material link to each other to provide strength, while the B components provide elasticity. Polymers of greater molecular weight are achieved by combining many of the A components in the A portions of each A-B-A structure and combining many of the B components in the B portion of the A-B-A structure, along with the networking of the A-B-A molecules into large polymer networks.
The elastomeric B portion of the example A-B-A polymers has an exceptional affinity for most plasticizing agents, including but not limited to several types of oils, resins, and others. When the network of A-B-A molecules is denatured, plasticizers which have an affinity for the B block can readily associate: with the B blocks. Upon renaturation of the network of A-B-A molecules, the plasticizer remains highly associated with the B portions, reducing or even eliminating plasticizer bleed from the material when compared with similar materials in the prior art, even at very high oil:elastomer ratios . . . .
The elastomer used in the example gel cushioning medium is preferably an ultra high molecular weight polystyrene-hydrogenated poly(isoprene+butadiene)-polystyrene, such as those sold under the brand names SEPTON 4045, SEPTON 4055 and SEPTON 4077 by Kuraray, an ultra high molecular weight polystyrene-hydrogenated polyisoprene-polystyrene such as the elastomers made by Kuraray and sold as SEPTON 2005 and SEPTON 2006, or an ultra high molecular weight polystyrene-hydrogenated polybutadiene-polystyrene, such as that sold as SEPTON 8006 by Kuraray. High to very high molecular weight polystyrene-hydrogenated poly(isoprene+butadiene)-polystyrene elastomers, such as that sold under the trade name SEPTON 4033 by Kuraray, are also useful in some formulations of the example gel material because they are easier to process than the example ultra high molecular weight elastomers due to their effect on the melt viscosity of the material.”
Other examples of gelastic material compositions are disclosed in other patents that identify Pearce as an inventor or Chen as an inventor (for example U.S. Pat. No. 5,336,708). The present invention is not directed toward the type of gelastic material being used. Instead the present invention is directed to how the gelastic material is formed and the desired shape of the material.
Cushion Material
Pearce also discloses the gelastic material can be formed into a cushion. The cushion may be used with many types of products, including furniture such as office chairs, “sofas, love seats, kitchen chairs, mattresses, lawn furniture, automobile seats, theatre seats, padding found beneath carpet, padded walls for isolation rooms, padding for exercise equipment, wheelchair cushions, bed mattresses, and others.” Selected cushion material is also dependent on the Indentation Load Deflection (ILD) measurement. The ILD measurement represents how much weight it takes to compress a cushioned material. The firmness of a piece of foam normally ranges from 10 to 100. The higher the ILD number the firmer the cushion material.
The thicker the cushion is, the firmer a particular type of cushion will feel. For example, where 2″ foam at 65 ILD will feel perfectly comfortable, 5″ foam at the same ILD will feel like you are sitting on a board. There is a general rule of thumb in deciding what firmness of foam to use in a given situation.
Seat Cushions:                2″ foam - - - 65 ILD        3″ foam - - - 40 ILD        4″ foam - - - 34 ILD        5″ foam - - - 30-34 ILD        6″ foam - - - 26-30 ILD        7″ foam - - - 20-26 ILD        
Back Cushions:                1″ foam - - - 30 ILD        2″ foam - - - 25-30 ILD        3″ foam - - - 20-25 ILD        4″ foam - - - 20 ILD        
These figures are only approximations.
Conventional Gelastic Cushion Structure
Pearce further states, “the cushioning element . . . includes gel cushioning media formed generally into a rectangle with four sides, a top and a bottom, with the top and bottom being oriented toward the top and bottom of the page, respectively. The cushioning element has within its structure a plurality of hollow columns . . . . As depicted, the hollow columns . . . contain only air. The hollow columns . . . are open to the atmosphere and therefore readily permit air circulation through them, through the cover . . . fabric, and to the cushioned object. The columns . . . have column walls . . . which in the embodiment depicted are hexagonal in configuration. The total volume of the cushioning element may be occupied by not more than about 50% gel cushioning media, and that the rest of the volume of the cushioning element will be gas or air. The total volume of the cushioning element may be occupied by as little as about 9% cushioning media, and the rest of the volume of the cushion will be gas or air. This yields a lightweight cushion with a low overall rate of thermal transfer and a [low] overall thermal mass. It is not necessary that this percentage be complied with in every instance.”
When a patient is positioned on the gelastic material, the patient's protuberances (the hip(s), shoulder(s), arm(s), buttock(s), shoulder blade(s), knee(s), and/or heel(s)) cause the column walls positioned below the patient's protuberances to buckle. Those buckled column walls are not supposed to collapse or fail because then the patient would bottom out on the underlying surface. Instead, the column walls positioned below and receiving the weight of the patient's protuberances buckle (bending and/or compressing) to redistribute and/or lessen the load of those buckled column walls to other column walls of the gelastic material. In other words, buckling the column (or side) walls permit the cushioning element to conform to the shape of the cushioned object while (a) evenly distributing a supporting force across the contact area of the cushioned object, (b) avoiding pressure peaks against the user, and (c) decreasing the chance of the patient bottoming out. Bottoming out, however, sometimes occurs.
Stepped Column Gelastic Cushion Embodiment
To address the occasional bottoming out problem, it is our understanding that Pearce disclosed numerous cushion embodiments to solve that problem. One cushion embodiment “depicts a cross section of a cushioning element using alternating stepped columns. The cushioning element . . . has a plurality of columns . . . each having a longitudinal axis . . . a column top . . . and a column bottom . . . . The column top . . . and column bottom . . . are open . . . , and the column interior or column passage . . . is unrestricted to permit air flow through the column . . . . The column . . . depicted has side walls . . . , each of which has three distinct steps . . . . The columns are arranged so that the internal taper of a column due to the step on its walls is opposite to the taper of the next adjacent column. This type of cushioning element could be made using a mold.”
A problem with Pearce's stepped column embodiment is that the side walls do not uniformly buckle due to the varied thicknesses. As previously stated, buckling the column (or side) walls permit the cushioning element to conform to the shape of the cushioned object while evenly distributing a supporting force across the contact area of the cushioned object and avoiding pressure peaks against the user. Buckling is difficult when the side walls are thick and tapered as disclosed in Pearce's stepped column gelastic material embodiment. The thicker portion of the walls do not decrease pressure peaks, instead the thicker portion of the walls maintain or increase the pressure peaks. Those pressure peaks are to be avoided and are not in Pearce's stepped column gelastic material embodiment.
Firmness Protrusion
Pearce also discloses a gelastic cushion having a firmness protrusion device positioned within the column walls to prevent the column walls from over-buckling (failing or collapsing so the patient bottoms out). In particular, Pearce wrote, “The cushioning element . . . has cushioning medium . . . formed into column walls. The column walls . . . form a column interior . . . . The column . . . has an open column top . . . and a closed column bottom . . . . In the embodiment depicted, the column . . . has a firmness protrusion . . . protruding into the column interior . . . from the column bottom . . . . The firmness protrusion . . . depicted is wedge or cone shaped, but a firmness protrusion could be of an desired shape, such as cylindrical, square, or otherwise in cross section along its longitudinal axis. The purpose of the firmness protrusion . . . is to provide additional support within a buckled column for the portion of a cushioned object that is causing the buckling. When a column of this embodiment buckles, the cushioning element will readily yield until the cushioned object begins to compress the firmness protrusion. At that point, further movement of the cushioned object into the cushion is slowed, as the cushioning medium of the firmness support needs to be compressed or the firmness support itself needs to be caused to buckle in order to achieve further movement of the cushioned object into the cushioning medium.” The firmness protrusion is a block of material designed to inhibit further buckling of the column walls. At best due to its shape and function, the firmness protrusion does not buckle.
Stacked Gelastic Cushion Embodiment
Another cushion embodiment is a stacked gelastic cushion embodiment which was claimed in U.S. Pat. No. 7,076,822. The stacked cushion embodiment as claimed has the following limitations:                “(a) a first cushioning element and a second cushioning element stacked together in sequence to form a stacked cushion,        (b) said stacked cushion having a stacked cushion bottom;        (c) said first cushioning element including                    (i) a quantity of first gel cushioning medium formed to have a first cushioning element top, a first cushioning element bottom, and a first outer periphery, said first gel cushioning medium being compressible so that it will deform under the compressive force of a cushioned object;            (ii) wherein said first gel cushioning media is flexible and resilient, having shape memory and being substantially solid and non-flowable at temperatures below 130° Fahrenheit;            (iii) a plurality of first hollow columns formed in said first gel cushioning medium, each of said first hollow columns having a first longitudinal axis along its length, each of said first hollow columns having a first column wall which defines a first hollow column interior, and each of said first hollow columns having two ends;            (iv) wherein each of said first column ends is positioned at two different points of said first longitudinal axis;            (v) wherein at least one of said first hollow columns of said first cushioning element is positioned within said first gel cushioning medium such that said first longitudinal axis is positioned generally parallel to the direction of a compressive force exerted on the stacked cushion by a cushioned object in contact with the stacked cushion;                        [sic] (c) wherein the stacked cushion is adapted to have a cushioned object placed in contact with said stacked cushion top; and        (d) wherein at least one of said first column walls of said first cushioning element is capable of buckling beneath a protuberance that is located on the cushioned object.”The stacked gelastic cushion embodiment is unstable unless the first cushioning element and the second cushioning element are secured to each other. Securing the two cushions together can be accomplished by adhesives and/or straps (rubber, cloth or equivalent) without fasteners (like a rubber band) or with fasteners (i.e., hook and loop, buckles and/or tying). The present invention avoids those securing devices because that increases the potential pressure peaks applied to the patient.How to Inhibit Gelastic Cushion from Moving        
The gelastic cushion is known to move in response to patient's applying a force to the gelastic cushion. To decrease that problem, the users of gelastic cushion have heated a non-woven material on the bottom surface of the gelastic cushion. That non-woven can cover the entire bottom surface or just a particular area including and not limited to being near and at the perimeter of the bottom surface.
The non-woven can also extend beyond the bottom surface's perimeter. The non-woven material that extends beyond the bottom surface's perimeter is then normally attached to another part of the cushion and that attachment decreases the chances that the gelastic cushion will move when the patient applies a force to it. This embodiment is very effective for controlling the position of the gelastic cushion but it results in the gelastic cushion hammocking the patient. One embodiment of the present invention solves this problem.